The phenomenon known as chemiluminescence involves the conversion of chemical energy into light energy. Chemiluminescence is involved in many chemical and biological processes, such as the bioluminescence of the firefly utilizing the enzymatic system containing luciferin and luciferase; however, the nature of this reaction is not well understood. Most of the chemiluminescent systems known to date involve the decomposition of peroxides. Peroxides are dangerous compounds which often decompose explosively. Therefore, there is a need for chemiluminescent compounds which do not decompose explosively. Luminescence is broadly defined as the emission of electromagnetic radiation. Some luminescent materials are called phosphors. While there are literally thousands of known phosphors, less than 100 are commercially manufactured on a large scale. Some phosphors are used in fluorescent lamps and others are used in speciality applications, such as cathode ray screens. Phosphors may be excited by infrared radiation, electric fields, chemical reactions and mechanical stress. However, most phosphors are excited by high energy photons or electrons.
The best known thermal decomposition of a pericyclic chemiluminescent reaction is that of the Dewar benzenes as described by N. J. Turro and V. Ramamurphy in "Rearrangements in Ground and Excited States," Vol. 3, Academic Press, New York, 1980, p. 15. However, in this case, the luminescence observed was not derived from the product itself, but from an added sensitizer, that is, these are sensitized chemiluminescent reactions. There is no known direct pericyclic chemiluminescent reaction of homocyclic compounds in the scientific literature. By this we mean that the thermal dissociation of heterocyclic compounds, such as dioxetanes, to generate n,.pi.* state involves the participation of n-orbitals and is not a chemiluminescent reaction of homocyclic compounds. The compounds of the present invention are homocyclic chemiluminescent compounds distinct from traditional phosphors and heterocyclic chemiluminescence.
The synthesis of benzene:anthracene cyclodimers shown below, results in a compound which exhibits reasonable stability under ordinary laboratory conditions. Yang, et al., J. Am. Chem. Soc., 104:953 (1982). The retrocycloaddition of the compound shown below (1a) results in two aromatic products rather than one and a decomposition which is not chemiluminescent. ##STR2##
Potentially these energy rich pericyclic benzene:anthracene cyclodimers, such as 1 a contain sufficient energy and are sufficiently stable to function as a source of chemical energy for the development of an efficient unimolecular chemiluminescent system. However, there is a need to develop modified structures which actually exhibit chemiluminescence. A system based on such modified structures would have applications in the development of an organic chemical lasing system or in any system requiring a chemical source of light.